This invention relates generally to incandescent illumination systems or fixtures and, more particularly, to incandescent lamps adapted for use in combination with a concave reflector in collecting a high proportion of the emitted light and projecting a high-intensity beam.
Incandescent lamps of this particular kind are useful in theater, television, architectural, and general purpose lighting fixtures that provide high-intensity beams of light. In such fixtures, it is desirable to collect as high a percentage of the emitted light as possible and to redirect that collected light as a high-intensity beam having a desired intensity distribution.
Incandescent lamps of this kind commonly are used in combination with ellipsoid or near-ellipsoidal reflectors. The lamps are positioned with their light-emitting filaments located at or near a general focal point close to the reflector, such that emitted light impinging on the reflector is redirected through a gate to a lens that then projects the high-intensity beam.
Alternatively, such lamps can be used in combination with parabolic or near-parabolic reflectors. The lamp is positioned with its filaments at or near the reflector's general focal point such that emitted light impinging on the reflector is redirected to form the projected beam without the need for a lens. However, a lens sometimes is used to alter the projected beam's divergence or spread or to integrate the beam and thereby provide a desired intensity distribution.
Incandescent lamps used in illumination systems of this kind typically have included a filament in the form of a large coiled coil having a longitudinal axis. The filament typically is oriented with its major axis parallel with the axis of an ellipsoidal reflector or perpendicular to the axis of a parabolic reflector.
Other incandescent lamps used in illumination systems of this kind have included a plurality of linear, helically-wound coils arranged in one or two parallel rows that form a light-emitting plane. These lamps typically have been used in combination with a spherical reflector, with their light-emitting plane facing away from, and toward, the reflector. Forwardly-emitted light is redirected by a lens to produce the high-intensity beam, while rearwardly-directed light is redirected by the reflector back toward the filaments, where it either is reabsorbed or is passed through the filaments to the lens to become part of the projected beam.
The incandescent lamps described briefly above have proven to be generally satisfactory for use in combination with concave reflectors in providing high-intensity beams of light. However, it is believed that these lamps are configured such that an excessively high proportion of their emitted light is not being collected and included in the projected beam. The wasted light either is emitted in directions not impinging on the reflector or is redirected by the reflector in undesired directions. This wasted light not only results in the projection of a beam of lower-intensity, but also requires that excess heat be dissipated and that additional, unused power be supplied to the lamp. This inefficiency also leads to the need for illumination systems or fixtures that are physically larger in size than is believed to be necessary.
It should, therefore, be appreciated that there is a need for an incandescent lamp having an improved arrangement of filaments such that the lamp can be used in combination with a concave reflector to project a high-intensity beam with a higher collection efficiency. The present invention fulfills this need.